Can Science Tell Us When Life Begins?

“Science” can tell us when life begins, provided that we already know what to look for. Empirical biology alone cannot tell us what that is. Once we establish a metaphysical account of life, then empirical embryology can tell us whether the relevant conditions are met.

Many pro-life commentators like to claim—as Senator Marco Rubio did recently—that the question of when human life begins is settled by “science.” In this essay, I will argue that while this claim is not exactly false, it is incomplete.

Though biological research must inform any serious philosophical judgment about the existence of human life, when human life begins is ultimately a question of metaphysics, not empirical biology. Thus, an adequate answer to the question requires us to consider not only what we think we know from contemporary empirical embryology, but also a robust philosophical account of what life is and at what point an individual human being can be said to exist. This, in turn, requires us to recognize something important about the relationship of the various sciences, not only the empirical ones such as biology, but also the speculative science of metaphysics.

The context of Senator Rubio’s remarks is instructive. He has courted charges of heresy against the magisterium of mainstream opinion by questioning anthropogenic accounts of climate change. He dug himself in further by suggesting hypocrisy on the part of some of his critics regarding their trust in “settled science” because they doubt that contemporary empirical embryology can establish that human life begins at conception. He told Sean Hannity that the “science is settled, it's not even a consensus, it is a unanimity, that human life begins at conception.”

The response from the mainstream media has been predictable, with supposed debunkings coming from both The Washington Post and The New York Times. At the Post, the headline cheekily declares, “Marco Rubio demanded people look at the science on abortion. So we did.” And, of course, what they “found” is a classic case of confirmation bias. They begin by disingenuously invoking the “scientific definition of pregnancy” as beginning with implantation. As I’ve recently argued here at Public Discourse, this is a complete red herring. The moral question about abortion concerns the killing of the child, not the termination of the pregnancy. Every caesarean section terminates a pregnancy but is not thereby an evil.

The Post article does note that there is a distinction between the beginning of life and pregnancy (without explaining why the author even brought up pregnancy) but concludes that “on the question of when life begins . . . the scientific experts [they] spoke with didn't offer any consensus.” It is then airily dismissed as “something of a philosophical question,” for “if someone were to argue that life begins at implantation, it’s hard to find a moral argument against forms of birth control that prevent that from happening.” Of course, many silly things follow from false claims, but that doesn’t make them interesting or plausible.

It’s at this point that we would do well to take a step back. For, in fact, there are elements of the truth on both sides here, but they’re being confused, whether deliberately or out of ignorance. Ultimately, I think, important questions are being begged all around.

Science, Philosophy, and Objective Truth

Why are so many pro-life advocates keen to claim that “science” can show when human life begins? The answer is simple: they want to invoke the considerable authority of contemporary “science” in our society, an authority that results from the scientists’ nearly uncontested claim to “objective truth.” By contrast, as the Post’s dismissal of Senator Rubio’s remarks makes clear, philosophical questions are often thought to be unanswerable, mere intellectual games, which cannot claim to be the source of genuine knowledge.

In short, since nearly everybody—left and right—agrees that “science” is “objective,” having the weight of “settled science” on one’s side has become practically the only trump card in highly contested debates of public policy. That’s exactly what’s going on in climate change debates as well, which is why the left is so keen to invoke the same authority. In many ways, this appeal to authority is just as misplaced in that context as in the abortion debate; while the findings of empirical science are clearly relevant in both contexts, they are not dispositive of public policy in either.

In fact, the Post and the Times are correct insofar as they note that the morality of abortion is a philosophical question, not a scientific one. However, neither really recognizes what all the relevant philosophical questions are, much less how to answer them. By contrast, many radical climate policy advocates fail to realize that whether or not human activity is a cause of climate change is a separate question from what, if anything, we should (or even can) do about it from a policy perspective.

With all of that said, on the abortion question, empirical science clearly does have something important to tell us. Empirical embryology can seek to determine when certain conditions are met that indicate the presence of a unique biological organism. On empirical grounds, embryologists such as Maureen Condic have argued that the overwhelming evidence suggests that these conditions are met at conception.

This is fine as far as it goes, but that doesn’t actually tell us when life begins. In fact, determining which criteria are the right criteria for ascertaining whether a living thing exists is not an empirical question at all. Instead, one’s answer to this question will turn on how one understands the nature of a living thing—i.e., on one’s metaphysics of life.

The Metaphysics of Life

In the final analysis, questions of existence are not, and cannot be, “scientific” questions, simply because they are not what empirical science is about. Speaking broadly, empirical science concerns physical change over time. However, as William Carroll has noted here at Public Discourse, “the change from non-living to living cannot be an observable transition, since the change occurs all at once, instantaneously.” Accordingly, this kind of instantaneous change is simply beyond the scope of empirical biology. Rather, this change is a substantial change; it involves an ontological transformation occurring not only on the level of matter, but also of form.

Furthermore, empirical biology as such cannot determine what life is, precisely because life is the proper subject of biology. The science of biology—i.e., the logos of bios (life)—must take living things for granted. As a special science (an organized body of knowledge about a specific topic), the scope of biology is predetermined by the scope of its foundational principles. In this case, those principles presuppose the existence of living things.

The Aristotelian way of thinking about the order of knowledge allows us to see that each of the lower sciences takes its principles from the higher sciences. So, for example, engineering takes its principles from physics, and, strictly speaking, an engineer qua engineer cannot question the principles of physics. This, of course, does not preclude an engineer from also becoming a physicist. Yet, insofar as he is a physicist, he no longer is acting as an engineer, and his science is no longer engineering.

This is a general point that leads to much confusion. In general, a particular person who happens, say, to be a biologist can also engage in philosophical reflection about the philosophy of biology, but insofar as she does, she does so not as a biologist, but as a philosopher. And if she is not careful to keep these separated, she can easily fall into the error of the craftsmen Socrates examined and found wanting in the Apology. Their problem was not that they knew nothing—they were masters of their crafts, after all—but rather that they thought they knew what they did not. Many contemporary scientists who wade into philosophical debates suffer the same fate. They tend to mistake the presuppositions of their sciences for the ultimate truth about the nature of things.

Accordingly, all of the special sciences are subordinate in their principles and must proceed under assumptions established by the highest science, metaphysics—the science of being qua being. With respect to biology, for example, metaphysics must establish what counts as a living thing. Once that is determined, the findings of empirical biology can and must inform judgments concerning the existence of a living thing. In the end, however, such judgments are properly philosophical, not biological.

Perhaps needless to say, the metaphysics of life is a deeply controverted question. In the traditional view, however, we can say that what fundamentally separates living things from non-living things is the fact that only living things have a good. So, it is only proper to say of living beings that things can go well or badly for them, because things can only go well or badly in terms of some good. Ultimately, what it means to say that things are going well for a living thing is simply that it exercises the powers that belong to it as a living thing (what have traditionally been called the “immanent” causal powers). This, then, is what separates living things from non-living things: the presence of powers such as taking in and metabolizing nutrients from the environment, growing and healing from injury, reproducing, etc. Only beings that do these kinds of things are alive.

When Does Life Begin?

So, from a metaphysical point of view, when does life begin? When an organism (i.e., substance) exists that manifests these sorts of immanent causal powers. When does human life begin? When an organism (substance) of a specifically human kind exists.

It’s here that the findings of contemporary empirical biology come into play. At conception, a new being comes into existence that exercises these sorts of powers, and we can know this by observing its activities. Furthermore, since that kind of being (a zygote) regularly (though not necessarily in every case) develops into a mature adult, we can know that it is a human being, an organism of the specifically human kind. So, yes, there is a sense in which “science” can tell us when life begins, provided that we already know what to look for. However, empirical biology alone cannot tell us what that is.

To return to the pro-life claim that “science” can tell us when life begins, I think we can allow that it is conditionally true, provided one understands that the biology is not telling us what life is, but whether or not we can observe certain signs that point to the underlying presence of immanent causal powers. In other words, once you have a metaphysical account of life, then empirical embryology can tell you whether the relevant conditions are met.

To get from empirical claims in embryology to a moral claim that abortion is wrong requires substantially more philosophical work. That work can be (and has been) done, but it is important to recognize just what kind of work it is and how much effort it really requires. We should seek to follow Socrates’ advice of cutting reality at the joints, keeping clear about the limits of the various sciences, including metaphysics, ethics, and biology.

Mathew Lu is Assistant Professor of Philosophy at the University of St. Thomas in St. Paul, MN.